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15 Cards in this Set
- Front
- Back
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what is a mutation?
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An alteration in the genetic material that can be inherited
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What is a gene mutation?
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an alteration in the nucleotide sequence gene
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What is a chromosome mutation?
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an alteration of chromosome structure or chromosome number
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What is a mutant?
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an organism or cell carrying one or more mutations. Mutations are rare(error frequency of 10^-5)...proof-reading...post-replicative DNA repair
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What are sources of mutations?
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1. spontaneous mutations ex: errors during replication, spontaneous lesions, repeat expansion
2. induced mutations (used in lab to create mutations) ex: chemicals like base analogs, intercalating agents, UV light, X-rays |
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What are indel mutations?
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the insertion or deletion of a small number of base pairs due to slippage during replication
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What are the four repair pathways?
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mismatch repair: couled to DNA replication; repairs mismatches created during DNA replication
Base Excision Repair: removes damaged base and replaces it with a good nucleotide Nucleotide Excision Repair: detects "bulky" damage and removes oligonucleotide harboring the damage. strand break repair: detects single-strand and double-strand breaks in DNA and stitches the strands back together. |
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What is the Hershey and Chase experiment?
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1. blender to break the bacteria away from the cell
2. centrifuge to separate them. The cells are heavier. p32 would be at the bottom, and S35 would be at the top |
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define point mutation? and indel mutations?
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just changing one base
2 kinds: transition and transversion small insertions or deletions result in: missense mutations, frameshift mutations, nonsense mutations (stop code comes too early) |
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Describe the mismatch repair process.
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MutS rotein recognizes the mismatch. It recruits MutL and MutH. The single-stranded cleavage near the mismatch on the newly replicated strand. Exonuclease removes the mismatch and surrounding nucleotides. DNA pol and DNA ligase fill the gap.
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What are the sources of DNA damaga?
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ionizing radiation, ultraviolet radiation, chemicals, oxidation
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What are the different pathways for repairing damaged DNA?
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Direct reversal of DNA damage( ex: photo-reactivated repair of pyrimidine dimers caused by UV light)
Excision repair pathways (recognition; removal; replacement) (base excision repair, nucleotide excision repair) error-prone repair pathways (damage is not removed but copied) strand-break repair (double-strand break repair) |
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Base Excision Repair
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It is initiated by an enzyme that recognizes a damaged base and removes it.
DNA glycosylase cleaves base-sugar bond; AP endonuclease makes the cut; dRpase removes a stretch of DNA; polymerasesynthesizes new DNA; ligase seals the nick |
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Nucleotide Excision Repair
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It recognizes the bulky distortion of the helix; removes the fragment containing the damage; replaces it by new synthesis of DNA
(Excision nuclease; DNA helicase; DNA polymerase and DNA ligase) |
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Double-strand break repair comes in two flavors. What are they?
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1. Direct rejoining of broken ends-called non homologous end-joining. Confined mostly to eukaryotic cells
2. Copying of broken sequence from sister chromatid in a cell that has a second good copy of the broken sequence following DNA replication called homologous recombination |
